Investigations are planned to clarify the nature and parameters of the two visual systems (focal and ambient) among neurological and ophthalmological patients and normals. In particular, the ability of subjects to utilize peripheral stimuli for orientation and localization without being aware of them consciously will be studied. These data will be utilized in the development of tests of localization (ambient) function which will supplement current perimetric procedures. Dependent measures will include circularvection, rollvection, postural stability and size constancy. The contribution of the ambient visual system to the phenomenon of autokinesis will be studied with respect to both visual and vestibular stimuli. In particular, we will investigate the extent to which peripheral visual stimuli can stabilize autokinesis, and when stability is obtained, the role of vestibular size stimulation. Research on accommodation will be planned to clarify the role of the autonomic nervous system and the possible influences of psychological and physiological stressors on the resting position of accommodation.